The present invention relates to the use of aminic azo dyes and their solutions in organic solvents, as pH depending markers of petrols, gas oils and generally for oil distillation products.
Petrols and gas oils are often additioned with small amounts, from 5 to 40 ppm, of liquid compositions of markers, in order to identify the oil product origin or for fiscal reasons.
The markers in many cases are constituted by liquid compositions of azoic dyes in organic solvents, which generally dye the oil products in yellow.
It is known that the marker control and its identification are carried out by treating a small amount of the oil product, depending on the marker, with an hydrophilic solution of a base or of an acid, which optionally can contain an organic solvent miscible with water.
The marker under these conditions undergoes a pH depending reaction with colour change. The extraction solutions assume more or less intense colorations, with a colour ranging from the red to the violet, to blue.
Among the commercial markers extractable in basic medium Mortrace(copyright) SB and ST (Morton) can be mentioned. Among those extractable in acid ambient, Sudan Marker(copyright) 455 (C.I. Solvent Yellow 124 -BASF) is known. This latter marker has an high absorbance as defined below, but it has the drawback to be synthetized with an industrially very expensive process, which besides the diazo-copulation reaction requires also an additional process step consisting in the condensation reaction with a vinylether.
Furthermore, other azoaminic markers extractable in acid medium, for example those described in the patent application WO 95/17483, are known. Tests carried out by the Applicant have shown that the azoaminic markers in which the nitrogen substituents are aliphatic groups, in the acid solution have a low specific absorbance E1%1 cm, defined as the absorbance referred to a solution at 1% w/v concentration in a 1 cm cell. See the Examples.
The need was felt to have available markers which in the extraction acid solution have high specific absorbance E1%1 cm characteristics at the respective wave length of maximum absorption, and obtainable with a simplified process.
The Applicant has unexpectedly and surprisingly found compounds to be used as markers of oil distillation product which overcome the above mentioned drawbacks.
It is an object of the present invention the use as markers of oil distillation product of amino azoic dyes having the general formula 
wherein:
R1 is linear or branched alkyl with a number of carbon atoms from 4 to 20;
R2 and R3 are independently H, CH3, C2H5, OCH3, OC2H5;
R4 and R5 are independently H, CH3, C2H5;
X is H, OH;
Y is hydrogen or the following poly-isopropoxy chain 
wherein n is comprised between 1 and 4; and of their concentrated compositions having a high dry titre in organic solvents, containing from 40 to 100% by weight of said azodyestuffs.
For the use according to the present invention preferably in the formula (I) compounds R1 is -C12H25 aliphatic radical or sec.butyl, the R2 and R3 substituents are independently from each other hydrogen, CH3, OCH3; R4 is hydrogen and X is hydrogen or OH, R5 is hydrogen, Y is H or the radical of formula 1a wherein n is comprised between 1 and 3
The organic solvent of the compositions having an high dry titre is selected from aromatic hydrocarbons having a number of carbon atoms from 7 to 15, optionally containing one or more C1-C4 aliphatic chains, and mixtures thereof, or solvents having a greater polarity than that of the above mentioned hydrocarbons, comprising in their molecule one or more functional groups containing oxygen, in which oxygen is bound by covalent bonds, such as for example ethers, alcohols, and/or with double bondxe2x95x900 such as for example esters, ketones, etc.
Examples of aromatic hydrocarbons usable as azodyes solvents are xylene, alkylnaphthalenes, the aromatic hydro-carbon mixture having from 10 to 11 carbon atoms known as Shellsol(copyright) AB; examples of solvents having a polarity greater than that of the aromatic hydrocarbons and comprising in the molecule one or more functional groups containing oxygen are 2-butoxyethanol, butylcellosolve acetate and diacetonalcohol.
According to the object of the present invention the compounds of formula (I) are extracted from the oil product by means of acid solutions of strong, inorganic and/or organic acids, having the following composition (% by volume):
from 5 to 90% of an aqueous solution of a strong acid, having a molarity equal to or higher than 0.5 M;
from 95 to 10% of an hydrosoluble organic solvent.
The extraction phase if necessary can be repeated more times in order to completely extract the marker. Examples of strong acids are halohalide acids, sulphuric acid, nitric acid, phosphoric acid; mono-, di-, tri-chloroacetic acid.
Examples of hydrosoluble organic solvents are alcohols such as methylic, ethylic, isopropylic alcohol; polyols as mono-, di-, polyethylenglycols, glycerine; ether-alcohols such as methoxy- ethoxy-, butoxy-ethanol; dimethylformamide, di-methylsulphoxide.
Optionally an additive can be added, soluble in the acid mixed aqueous/organic phase used for the extraction, to decrease the background coloration of the extraction solution. For example a salt in amount from 5 to 20% w/v can be used. Examples are KCl, CaCl2, ZnCl2, ZnSO4, AlCl3.
In the extraction tests carried out by the Applicant to show the advantages obtainable with the use of the present invention markers, in a first series of tests, solutions obtained by diluting in isooctane the marker concentrated liquid compositions up to concentration 5-20 ppm, have been used. These yellow-coloured solutions have a wave length at the absorption peak xcexmax in the range 395-410 nm. The extraction acid solutions have a magenta red colour with xcexmax in the range 530-545 nm. The tests reported in the examples show that the invention markers in the extraction acid solutions have a very high specific absorbance E1%1 cm, the concentration of the azoic compound being equal, in particular higher than 50%, in comparison with the above mentioned azoaminic markers.
For example the specific absorbance E1%1 cm of the N-ethyl-N- (2-hydroxyethyl)-4-[(dodecylphenyl)-azo]-m-toluidine compound, in concentrated liquid composition at concentration 0.1 moles/70 g, is 775 (xcexmax=538 nm) in the acid hydroalcoholic solution used for the extraction (HCl 10N/ethanol 50/50 v/v), while the one of the composition containing N,N-diethyl-4-[(dodecylphenyl)-azo]-m-toluidine is 424 (xcexmax=535 nm). See Table 1 (in the Table the marker concentrations in the concentrated liquid compositions are 0.1 mole/70 g of composition, calculated by supposing a synthesis yield of
In a second series of tests the marker concentrated compositions have been added to the oil product (gas oil for autotraction, see the Examples) to give marker concentrations in the range 0.5-10 ppm. The extraction has been carried out as described above. The extraction solution coloration moves towards xcexmax values lower than the previous ones, up to about 480 nm, towards the red and orange since the background colour is present. However the peak corresponding to the maximum absorption wave length results clearly identifiable also under these conditions.
Without to be bound to any theory, the Applicant thinks that the greater specific absorbance of the markers of the present invention is due to the association between the hydroxyl group which are in the nitrogen substituent aliphatic groups of these compounds and the organic solvent in the extraction solution.
The markers of the present invention have in the extraction solvent an high absorbance comparable, the concentration being equal, with that of Sudan Marker(copyright) 455. However the present invention markers are obtainable with a simpler process, as described hereinunder.
It has been found by the Applicant that formula (I) compounds wherein R1=C4H9, are extractable also with aqueous acids (ex. HCl 5N). However the solution coloration intensity is lower than that obtained in an aqueous solution in admixture with an organic water-soluble solvent.
The preferred markers are those wherein R1 of formula (I) is a linear or branched alkyl having from 6 to 20 carbon atoms, said compounds having a specific absorbance E1%1 cm in the mixed aqueous/organic extraction solution higher than those markers wherein R1=C4 alkyl. See Table I.
The present invention markers, or the corresponding compositions in organic solvents having a high dry titre, are added to the oil distillation products in amounts from 0.5 to 50 ppm.
The present invention markers can be used in admixture with other markers and/or dyes used in this field, which are selected among those which do not interfere in the described extraction process.
It is a further object of the present invention compounds of formula (IX): 
wherein:
R1 is linear or branched alkyl with a number of carbon atoms from 6 to 20;
R2, R3, R4 and R5, X and Y are as defined in formula (I).
Said dyes, besides having the advantageous spectrophotometric properties above said over those of the compounds of the same formula wherein R1=C4 alkyl, are not extracted with aqueous acids. This properties make it possible their use in combination with a blue dye as additives to make petrol green-coloured under the provisions of the Italian Ministerial Decree 6.3.97, that states that said dyes must not be extractable with aqueous acids.
The compounds of formula (I) are synthetized by starting from primary aromatic amines mono-alkyl substituted in the ring and by tertiary aromatic amines N,N disubstituted with alkylic chains containing at least an hydroxyl group.
The aromatic aminic copulating agent for obtaining the compounds of formula (I) when Y is the radical of formula (IA), is prepared by reacting the aromatic amine having one branched alkyl group of formula: xe2x80x94CH2xe2x80x94CH(R5)xe2x80x94OH with the requested number of moles of 1,2-propylene oxide, at a temperature comprised between 140-170xc2x0 C., in the presence of a base catalyst, such as KOH, CH3ONa, etc.).
The raw materials are easily available on the market. Furthermore, the hydroxylated tertiary aromatic amines used in the present synthesis are not classified as toxic.
The process to obtain the markers, and which allows to obtain contemporaneously also the respective concentrated compositions having a high dry titre in organic solvents, comprises the following steps:
1) diazotization, in hydroalcoholic solution of isopropyl alcohol, with nitrous acid of the primary aromatic amine having the R1 group and obtainment of the corresponding diazonium salt;
2) diazonium salt copulation with the aromatic amine N,N disubstituted with alkyl chains containing at least one hydroxyl group, at 0xc2x0 C. and at pH between 2 and 5 buffered with a sodium carbonate or a sodium acetate solution, in the presence of an aromatic solvent as defined, from which the formed product is extracted;
3) Recovery of the solution in the organic solvent having a high dry titre ready to be use.
Alternatively to step 3) the solvent can be evaporated at reduced pressure and the product is obtained.
At the end of step 2), after isopropyl alcohol recovery and elimination of the aqueous phase by siphoning, the organic phase is concentrated under vacuum at 115-120xc2x0 C. and clarified by filtering on sintered filter having an average porosity (G3 porosity). If the final solution is too viscous, the clarification by filtering is carried out before the concentration phase.